The importance of PLATO observations for pre-main sequence asteroseismology
Abstract
Space observations of pre-main sequence stars allow investigating the earliest phases of stellar evolution which are crucial for our understanding of the complete life cycle of stars and the formation of planets. In recent years, we have demonstrated that the pulsation frequencies can be used to trace the early evolutionary history of the stars and that the formation process leaves a traceable imprint on the stars' interior structures until the onset of hydrogen core burning. This illustrates the importance of pre-main sequence asteroseismology. Currently, more than 130 pre-main sequence p- and g-mode pulsators of six different types with masses from about 1.2 to 5 solar masses are known. The majority of these stars have comparatively short photometric time series of up to 100 days length observed by the MOST, CoRoT, Kepler K2 and TESS space missions. PLATO will for the first time offer the opportunity to deliver light curves of pre-main sequence stars with time bases of two years or more. In my talk, I will focus on the next theoretical and observational steps in pre-main sequence asteroseismology in context to the future PLATO observations.
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TASC9/KASC16 Workshop, ISTA 2025 THE IMPORTANCE OF PLATO OBSERVATIONS FOR PRE-MAIN SEQUENCE ASTEROSEISMOLOGY Konstanze Zwintz Universität Innsbruck, Institute for Astroand Particle Physics © T. Steindl Credit: ESA/ATG medialab
K. ZwintzTASC9/KASC16 Workshop, ISTA 2025 2 Stars do not “pop up” on the main sequence!
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz THE IMPORTANCE OF EARLY STELLAR EVOLUTION From the 1950ies and 1960ies… 3 1961PASJ...13..450H Hayashi (1961)
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz 1961PASJ...13..450H THE IMPORTANCE OF EARLY STELLAR EVOLUTION …until today 4 Hayashi (1961) With constant accretion 2 M⦿ star With disk-mediated accretion Steindl, Zwintz, Vorobyov (Nature Com., 2022) Based on Hayashi (1961)
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz 103104105106107108109 star age (yr) 0.0 0.5 1.0 1.5 2.0 enclosed mass (MØ) a Burning regions ( erg g°1s°1) >10 >102>103>104 Mixing regions radiative convective overshoot 103104105106107108109 star age (yr) 0.0 0.5 1.0 1.5 2.0 enclosed mass (MØ) b THE IMPORTANCE OF EARLY STELLAR EVOLUTION Change of interior structure 5 Steindl, Zwintz, Vorobyov (Nature Com., 2022) Deuterium burning Deuterium burning Following Hayashi (1961) & Henyey (1955) 2 M⦿ star With disk-mediated accretion
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz THE IMPORTANCE OF EARLY STELLAR EVOLUTION Different structure detectable with pulsations 6 Comparison to observational precision: 4-year data by Kepler 1-year data by TESS 3.43.53.63.73.83.94.0 log(TeÆ) °1.0 °0.5 0.0 0.5 1.0 1.5 2.0 2.5 log(L/LØ) a model number 1 7 13 15 18 25 27 33 0.000 0.005 0.010 0.015 b 1 2 3 4 5 6 7 8 9 10 11 12 13 15 radial order n 0.000 0.005 c frequency diÆerence f°fclassic (d°1) pre-MS ZAMS 2 M⦿ star Steindl, Zwintz & Vorobyov (Nature Com., 2022)
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz THE IMPORTANCE OF EARLY STELLAR EVOLUTION Different structure detectable with pulsations 7 Comparison to observational precision: 4-year data by Kepler 1-year data by TESS 3.43.53.63.73.83.94.0 log(TeÆ) °1.0 °0.5 0.0 0.5 1.0 1.5 2.0 2.5 log(L/LØ) a model number 1 7 13 15 18 25 27 33 0.000 0.005 0.010 0.015 b 1 2 3 4 5 6 7 8 9 10 11 12 13 15 radial order n 0.000 0.005 c frequency diÆerence f°fclassic (d°1) pre-MS ZAMS Stars do NOT “forget” their past! 2 M⦿ star Detectable frequency differences from treatment of pre-MS evolution up to the ZAMS " (and even beyond) Steindl, Zwintz & Vorobyov (Nature Com., 2022)
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz PRE-MS PULSATORS Known types in the HRD 8 log Teff [K] log L/L⦿ Spectral type Kurtz (2022) ~18 Slowly Pulsating B (SPB) > 100 δ Scuti ~8 γ Doradus ~4 Hybrid pand g-mode pulsators 1 Tidally perturbed Solar-like: 1 candidate M types: 1 candidate Approximate numbers (likely incomplete)
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz INSTABILITY STRIPS FOR PRE-MS STARS Based on accreting stellar evolution models 9 ZAMS Accreting track
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz PRE-MS ASTEROSEISMOLOGY Observational status now 16 •Available data for pre-MS stars -MOST and CoRoT: max 40 days -No Kepler main mission -Some Kepler K2: max. 80 days -TESS: max. 100 days ‣Crowding issues in galactic plane •Limited time bases: < 100 days •Cadences: mostly 30-minutes Fig. 18 Illustration of PLATO FoVs (blue) in comparison to Kepler (pink), K2 fields (green) and CoRoT mission fields (red). Lines indicate the TESS viewing zones. The position of the PLATO fields is indicative only (figure re-produced from Nascimbeni et al 2022). observing scenario therefore splits the 4 years science observation phase into 2 observing blocks of 2 years each, so-called long-pointings (LOPs). Alternative scenarios are possible, e.g. a longer field of 3 years duration followed by a phase of shorter stepand-stare pointings (SOPs). Another possible scenario would be, for example, to stare at one field only for the whole science operation phase. The spacecraft provides the technical flexibility to choose from such scenarios, and even adapt the strategy during the science operation phase if needed. The PLATO Input Catalogue (PIC) for first pointing of the satellite must be defined by ESA�s PLATO SWT at the latest 2 years before launch. An update is planned for 9 months before launch, including the definition of the so-called "prime sample" (see Section 6). The subsequent target fields and their "prime sample" members are defined 6 months before the start of each field. Once this mission is completed and in case an extended mission is granted, another evaluation for key regions which would deserve dedicated PLATO pointings can be made, unless extended observations of already covered fields are given priority. PLATO target sky regions are constrained by the mission science requirements defining the stellar samples to be observed (see Section 6)aswellastechnicalconstraints (e.g. Sun avoidance angles). In fact it turned out that due to the large field 73 Nascimbeni et al. (2022)
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz PRE-MS ASTEROSEISMOLOGY PLATO as game changer 17 Credit: V. Nascimbeni, PIC Team LOPS2
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz PRE-MS ASTEROSEISMOLOGY PLATO as game changer 18 β Pictoris LOPS2
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz PRE-MS ASTEROSEISMOLOGY PLATO as game changer 19 •PLATO LOPS2: - Several hundreds of pre-MS stars! - Young clusters! - Star forming regions! •Time bases > 700 d •Shorter cadences •Pixel scale: 15” x 15” " → less crowding issues β Pictoris LOPS2
TASC9/KASC16 Workshop, ISTA 2025 K. Zwintz THE IMPORTANCE OF PLATO FOR PRE-MS ASTEROSEISMOLOGY •Period-spacing patterns ➜ Angular momentum transport studies •Increase numbers of pre-MS pulsators ➜ Mapping the early evolution history of pulsators •Contribution to more accurate ages for stars in general •Potential bona-fide discovery of “a young Sun” (see J. Jørgensen’s talk) •Contribution to a better description of stellar evolution What PLATO will do for this research field 20